[Early detection and intervention of hearing impairment in Cuba: outcome after 20 years]. / Diagnóstico e intervención temprana de los trastornos de la audición: una experiencia cubana de 20 años

INTRODUCTION: Infant hearing loss is a highly prevalent disorder which untreated can severely disrupt normal brain development. As a result there is a significant delay in language acquisition as well as many cognitive and emotional problems in the child. Over the last decades important advances have occurred in the available technology for early detection and assessment of hearing impairment. Therefore many countries worldwide have become aware of the need for hearing screening programs. The optimal protocols depending on the local conditions of health care as well as the availability of technological and human resources. AIM: To summarize the results obtained over the last 20 years by an ongoing hearing screening protocol. DEVELOPMENT: Data on the coverage program, sensitivity and specificity, age of identification of hearing losses, diagnostic and intervention stages will be summarized and discussed. Also the long terms effects of early detection on the child cognitive and language development are analyzed. Finally, the possible role of a new technique based on the recording of multiple auditory steady state potentials with Cuban equipment (AUDIX system) was evaluated within this context. CONCLUSIONS: The Cuban targeting multiple high risk hearing screening program is a useful alternative to early detection of hearing losses. The average detection age of hearing loss was 10 months during the period of optimal functioning. Cognitive, emotional and linguistic development are improved by early detection and intervention. The multiple auditory steady state responses can provide valuable audiometric information within a screening context.

[Neuropsychological study of 8 to 15-year-old children with lateralised sub-clinical paroxysmal discharges and poor academic achievement]. / Estudio neuropsicológico de niños de 8 a 15 años que presentan descargas paroxísticas subclínicas lateralizadas y bajo rendimiento escolar.

Paroxysmal discharges have been observed in non epileptic children who, at the same time, display learning disorders. In this study our aim is to determine whether the association between sub clinical discharges (SCD) and learning disorders reflects specific neuropsychological deficiencies and, more particularly, whether the possible deficits are defined according to the brain hemisphere in which the paroxysmal activity is located. Neuropsychological evaluation was performed in 17 children between the ages of 8 and 15, with unspecific learning disorders, who presented sub clinical paroxysmal discharges localised in the left hemisphere (nine cases) or in the right hemisphere (eight cases). The children with paroxysmal activity in the left hemisphere obtained similar results to those in which it was found on the right, except in the tests that evaluate visuo constructive skills, in which their scores were higher, and in the executive function tasks, in which they displayed a deficit that was not observed in the children with paroxysmal activity in the right hemisphere. We interpreted the presence of SCD discharges in the left hemisphere as reflecting a slower or more deficient process of brain maturation, which could be compensated with a suitable programme of neuropsychological intervention.

Normativa para la realización e interpretación de potenciales evocados visuales en edades pediátricas / Standards for carrying out and interpreting visual evoked potentials in children

Introducción. Un paso previo indispensable para la introducción en la clínica pediátrica de los potenciales evocados visuales (PEV) provocados por estimulación con diodos emisores de luz (LED) es su caracterización a través de las diferentes etapas de maduración del sistema nervioso. Pacientes y métodos. Hemos obtenido PEV a LED en una muestra de 60 niños de entre 1 y 5 años, funcionalmente sanos, distribuida homogéneamente por edad y sexo. En cada niño se registraron las respuestas a la estimulación monocular (derecha e izquierda), binocular y sin estimulación (réplicas de cada condición). Los registros se realizaron bajo sedación con secobarbital a 3 mg/kg de peso corporal. Resultados. De acuerdo con nuestros resultados se comprueba una reducción significativa de la latencia de todos los componentes (excepto P3) y de la amplitud de N1 y P1 en función de la edad. La respuesta a LED es replicable (sobre todo intraindividuos), observándose hasta tres variantes morfológicas. La sedación no afectó la detectabilidad de la respuesta, el único efecto significativo fue una reducción de la amplitud de P1. Conclusiones. Comprobamos cambios maduracionales, reflejados en la reducción significativa de los valores de latencias de la mayoría de los componentes con el incremento de la edad, alcanzándose valores similares al adulto entre los 4 y 6 años de edad. Los resultados obtenidos nos brindan la posibilidad de difundir estos datos normativos para una mejor utilización e interpretación de los PEV a LED a edades tempranas(AU)

Introduction: An essential step, prior to the introduction into paediatric practice of visual evoked potentials (VEP) caused by stimulation with light emitting diodes (LED) is their description at different stages of maturity of the nervous system. Patients and Methods: We obtained VEP to LED in a group of 60 children aged between 1 and 5 years, who were functionally healthy and equally distributed with regard to age and sex. In each case we recorded the responses to monocular stimulation (right and left), binocular stimulation and without stimulation (replicas of each condition). The recordings were made under sedation with secobarbital at a dose of 3 mg/kg body weight. Results: Our results showed a significant reduction in the latency of all components (except P3) and the amplitude of N1 and P1, as a function of the age of the child. The response to LED is reproducible (especially intra-individual) with up to three types of morphology observed. Sedation did not affect detection of the response. The only significant effect was a reduction in the amplitude of P1. Conclusions: We confirmed the changes due to maturity, reflected in a significant reduction of the latency of most components with increasing age. By between 4 and 6 years old the figures obtained were similar to those in adults. The results obtained give us the opportunity chance of publishing this standard data so that better use and interpretation of VEP to LED at an early age may be possible(AU)

Introdução. Um passo inicial indispensável para a introdução, na clínica pediátrica, dos potenciais evocados visuais (PEV) provocados por estimulação com díodos emissores de luz (LED), é a sua caracterização através das diferentes etapas de desenvolvimento do sistema nervoso. Doentes e métodos. Obtivemos PEV por LED numa amostra de 60 crianças com idade compreendida entre 1 e 5 anos, distribuída homogeneamente por idade e por sexo. Em cada criança registaram-se as respostas à estimulação monocular (direita e esquerda), binocular e sem estimulação (réplicas de cada condição). Os registos realizaram-se sob sedação com secobarbital a 3 mg/kg de peso corporal. Resultados. De acordo com os nossos resultados, é comprovada uma redução significativa da latência de todos os componentes (excepto P3) e da amplitude de N1 e P1 em função da idade. A resposta ao LED é reprodutível (sobretudo intra?indivíduos), sendo observada em três variantes morfológicas. A sedação não afectou a detecção da resposta, sendo o único efeito significativo, uma redução da amplitude de P1. Conclusões. Comprovamos alterações de desenvolvimento, que se reflectem na redução significativa dos valores de latências da maioria dos componentes, à medida que a idade aumenta, sendo alcançados valores similares aos dos adulto entre os 4 e os 6 anos de idade. Os resultados obtidos não permitem difundir estes dados normativos para uma melhor utilização e interpretação dos PEV por LED em idades baixas(AU)

Steady state responses to multiple amplitude-modulated tones: an optimized method to test frequency-specific thresholds in hearing-impaired children and normal-hearing subjects.

OBJECTIVE: To evaluate, using statistical methods, the usefulness of the binaural multiple frequency auditory steady state responses (MF SSRs) for objective, frequency-specific audiometry in a large sample of hearing-impaired children and normal-hearing subjects. DESIGN: The MF SSRs were recorded in a sample of 43 hearing-impaired children (86 ears) and 40 normal-hearing young adults (80 ears). Simultaneous carrier tones (0.5, 1, 2, and 4 kHz) modulated in amplitude at different rates (77 to 105 Hz) were presented binaurally (TDH 49 earphones) at variable intensities (110 to 20 dB SPL). For each subject the response thresholds (RTHs) at 0.5, 1, 2, and 4 kHz, were determined automatically (F test) and compared with the corresponding behavioral thresholds (BTHs). RESULTS: In the normal-hearing subjects, RTHs were detectable, on average, between 11 and 15 dB above the BTH. These differences were significantly smaller in the hearing-impaired (5 to 13 dB). Also a close correspondence was found between the subjective and objective audiogram curves in both groups. The within subject Spearman correlation coefficients calculated between the two curves, were in most cases above the significance cut off point (p < 0.05). Also in 1-way repeated measures analysis of variance, the overall error in the estimation of the audiogram (vector across frequency of absolute distances between the curves) did not differ significantly from zero. CONCLUSIONS: The binaural MF SSR was proven to be a valid technique for the estimation of an objective audiogram, in a large sample of hearing-impaired children and normal-hearing subjects. With this method, frequency-specific thresholds at 0.5, 1, 2, and 4 kHz could be determined in all subjects (and both ears) with no appreciable loss in accuracy and a considerable reduction in testing time (average recording time = 21 minutes) when compared with other frequency-specific techniques.

[Standards for carrying out and interpreting visual evoked potentials in children]. / Normativa para la realización e interpretación de potenciales evocados visuales en edades pediátricas.

INTRODUCTION: An essential step, prior to the introduction into paediatric practice of visual evoked potentials (VEP) caused by stimulation with light emitting diodes (LED) is their description at different stages of maturity of the nervous system. PATIENTS AND METHODS: We obtained VEP to LED in a group of 60 children aged between 1 and 5 years, who were functionally healthy and equally distributed with regard to age and sex. In each case we recorded the responses to monocular stimulation (right and left), binocular stimulation and without stimulation (replicas of each condition). The recordings were made under sedation with secobarbital at a dose of 3 mg/kg body weight. RESULTS: Our results showed a significant reduction in the latency of all components (except P3) and the amplitude of N1 and P1, as a function of the age of the child. The response to LED is reproducible (especially intra individual) with up to three types of morphology observed. Sedation did not affect detection of the response. The only significant effect was a reduction in the amplitude of P1. CONCLUSIONS: We confirmed the changes due to maturity, reflected in a significant reduction of the latency of most components with increasing age. By between 4 and 6 years old the figures obtained were similar to those in adults. The results obtained give us the opportunity chance of publishing this standard data so that better use and interpretation of VEP to LED at an early age may be possible.

Comparison of statistical indicators for the automatic detection of 80 Hz auditory steady state responses.

OBJECTIVE: To evaluate, using receiver operation characteristic (ROC) curves, the performance of several statistical indicators in the objective detection of 80 Hz steady state auditory evoked responses. DESIGN: Steady state auditory evoked responses elicited by amplitude modulated tones of 500 and 1000 Hz, were obtained in 16 normal adults. Recordings were made at intensities ranging from 80 to 30 dB SPL and without stimulation. Four statistics: coherence synchrony measure, circular T2, a new variant of Hotelling T2 (labeled HT2) and a test for hidden periodicity (F test) were calculated. The statistics were compared using ROC curves and bootstrapping techniques. Two outcome measures were considered: behavioral threshold prediction and averaging efficiency. RESULTS: All indicators were highly accurate to detect a response (8 to 9 dB above mean behavioral threshold for the 1000 Hz and 14 to 16 dB for the 500 Hz carrier). Responses could be reliable detected after averaging about five individual epochs of long duration. No statistically significant differences were evidenced though in their capability to predict behavioral threshold or their averaging efficiency. CONCLUSIONS: Despite the more adequate statistical properties of some of these indicators no significant differences were found in their performance. Thus all of these indicators could be recommended for automatic detection of 80 Hz auditory steady state responses.

Testing topographic differences between event related brain potentials by using non-parametric combinations of permutation tests.

MANOVA and repeated measures ANOVA approaches have provided evidence of a number of limitations in several event-related potential (ERP) studies due to violations of their statistical assumptions and the typically moderate size of the available sample. Alternative, computer-intensive methods based on permutation principles have recently been developed. Up to now this methodology has focused mostly on magnitude differences between scalp distributions as measured by t statistics. In this paper the scope of permutation techniques in ERP analysis was widened. A new statistic (D statistic) is introduced to compare the shapes of scalp distributions of ERPs. Additionally a general non-parametric combinatory technique is introduced to evaluate, by means of multivariate permutation tests, several time points and/or recording sites in ERP data. The methodology described here was used to test if two ERP components elicited during word-pair matching tasks to semantic or phonological incongruences had different scalp distributions.

Frequency-specific audiometry using steady-state responses.

OBJECTIVE: To evaluate the audiometric usefulness of steady-state responses to multiple simultaneous tones, amplitude-modulated at 75 to 110 Hz. DESIGN: Steady-state responses to multiple tones amplitude-modulated at different rates between 75 and 110 Hz and presented simultaneously were recorded at different intensities in normal adults, well babies, normal adults with simulated hearing loss, and adolescents with known hearing losses. Response thresholds were compared with behavioral thresholds. RESULTS: In normal adults the thresholds for steady-state responses to tones of 0.5, 1, 2, and 4 kHz were 14 +/- 11, 12 +/- 11, 11 +/- 8, and 13 +/- 11 dB, respectively, above behavioral thresholds for air-conducted stimuli, and 11 +/- 5, 14 +/- 8, 9 +/- 8, and 10 +/- 10 dB above behavioral thresholds for bone-conducted stimuli. In well babies tested in a quiet environment, the thresholds were 45 +/- 13, 29 +/- 10, 26 +/- 8, and 29 +/- 10 dB SPL. In adolescents with known hearing losses, the steady-state responses thresholds predict behavioral thresholds with correlation coefficients (r) of 0.72, 0.70, 0.76, and 0.91 at 0.5, 1, 2, and 4 kHz, respectively. CONCLUSION: Steady-state responses to tone amplitude-modulated at 75 to 110 Hz can be used for frequency-specific objective audiometry. The multiple-stimulus technique allows thresholds to be estimated for eight different stimuli at the same time.

Brain potentials and the availability of semantic and phonological codes over time.

ERPs were recorded from subjects performing semantic and rhyme matching tasks using either spoken words, printed words or pictures as stimuli. Mismatches enhanced N400 (in the semantic task) and N450 (in the rhyme task). Onset and peak latencies were shorter for N450 than for N400 with spoken words; this relationship was inverted for pictures. Thus these latencies could index availability of semantic and phonological codes. For printed words, the latencies were shorter for N400 than N450, a result that supports direct-access modes of reading with late phonological code activation. The longer latencies found for N400 and N450 to pictures could suggest longer initial decoding for pictures with respect to words.

Maximum likelihood estimation of signal detection model parameters for the assessment of two-stage diagnostic strategies.

The methodology of Receiver Operating Characteristic curves based on the signal detection model is extended to evaluate the accuracy of two-stage diagnostic strategies. A computer program is developed for the maximum likelihood estimation of parameters that characterize the sensitivity and specificity of two-stage classifiers according to this extended methodology. Its use is briefly illustrated with data collected in a two-stage screening for auditory defects.

Different functional properties of on and off components in auditory brainstem responses to tone bursts.

Auditory brainstem responses to tone bursts of constant rise and fall time and variable plateau were obtained in 7 normal hearing adults with a vertex to mastoid electrode configuration. In all records, two vertex-positive components (A, B) were present. Peak A is probably an onset response. Peak B latency increased linearly with plateau duration (r = 0.93) and seems to be an off response. White and notched acoustic noise masking had a different effect on the two components. A greater latency shift was observed for peak A than for peak B, thus reducing the interpeak interval in the masked response. When using high-pass noise, as we lowered the cut-off points from 4 to 0.5 kHz, there was also a greater latency increment for peak A than for peak B. These results suggest a more apical cochlear origin for the off response.

Comparison of auditory-evoked potential detection methods using signal detection theory.

The performance of statistical evoked-potential detection methods was compared with that of human observers and among themselves by means of receiver operating characteristics (ROC) curves. The test material was a collection of brain stem auditory-evoked responses obtained from 98 infants with 60 and 30 dB nHL clicks. The observers and the statistical methods had to discriminate these responses from control recordings obtained without acoustic stimulation. Although the observers' criteria on different days varied considerably, the discrimination capacity was more stable. The discrimination capacity depended on the observers' experience. The statistical methods tested were the correlation coefficient (CCR), the standard deviation ratio (SDR) and a new method named T2R. The most efficient detection method was T2R. For false-alarm rates of 0.01 the statistical methods were more efficient than the human observers. Signal detection theory is useful for the evaluation of evoked-potential analysis methods.